...also, get some Brick banding and clean the crust off the brass pistons. Squeeze the lever until the piston is far out as you dare, then clean the crust off. You will be able to push the piston back in with finger pressure.
If you don't clean the crust off and put new pads in then the crust will be pushed behind the rubber washer inside the caliper, this will rupture the washer and the calipers will leak brake fluid.